Modulation of Radiation-Induced Apoptosis

Many of the agents that are used in cancer therapy, including ionizing radiation and hyperthermia, can induce apoptosis. This chapter describes some of the signaling pathways that are thought to be involved in apoptosis and several strategies for modification of radiation-induced apoptosis that target these signaling mechanisms. Cells exposed to ionizing radiation become arrested at various stages in the cell cycle. A rapidly expanding family of genes have been isolated that share sequence homology to bcl-2. Changes in bcl-2 expression may explain some of the observations of modulation of the susceptibility to apoptosis by differentiation. Cytoplasmic serine and cysteine proteases play an important role in the execution of the apoptotic program. Suramin, a synthetic polysulfonated anionic compound, originally used as an antiparasitic agent, is cytostatic to a variety of tumor cells. apoptosis occurs in cells that have sustained cellular damage or cells that are required to die. Aberrant cell survival resulting from inhibition of apoptosis may contribute to oncogenesis.